Dentifrice compositions containing surface-active n-(2-hydroxyalkyl)-n-methyltaurine-n-oxide



United States Patent M This invention relates toN-(2-hydroxyalkyl)-N-methyltaurine-N-oxides, alkali metal salts thereof,and methods of preparation. The invention additionally relates todetergent and dentifrice compositions containing N-(Z-hydroxyalkyl)-N-methyltaurine-N-oxides and alkali metal salts thereof asactive ingredients.

The compounds,

where R is an alkyl group having from 8 to 18 carbon atoms, and M isselected from the group consisting of hydrogen and alkali metals, havebeen discovered.

The novel compounds of this invention are excellent surface activeagents, and are useful in detergent and dentifrice formulations. TheN-(Z-hydroxyalkyl)-N-methyltaurine-N-oxides show detergencycharacteristics, both alone and in the presence of conventional buildersalts, such as alkali metal sulfates, carbonates, silicates, phosphates,borates, and mixtures thereof. The presence of conventional detergentbuilders generally improves the detergency of the compositions.Additional components, such as carboxymethylcellulose, which improvesthe dirt suspending properties of the washing solution, may be used.Also, other synthetic detergents, soaps, perfumes, abrasives, foamstabilizers, germicidal agents, coloring agents and the like, may beincluded in the detergent com positions of this invention. Accordingly,they are useful in dish washing detergents, non-soap bars, soap bars,bars containing mixtures of soaps and non-soaps, shampoos, and to otherapplications known to those skilled in the art where surface activeproperties are desired.

As will be noted below, another significant advantage of the compoundsof this invention is that the compounds within the series having thebest detergent characteristics are those Where R has a chain length of13 to 18 carbon atoms, and can thus be obtained from less expensive rawmaterials.

The N-(Z-hydroxyalkyl)-N-methyltaurine-N-oxides of this invention areparticularly useful in dentifrice compositions, such as toothpaste.These compounds produce a large amount of foam, and do not lose theirfoaming power during the normal storage period while the compound is incontact with the other toothpaste ingredients. By comparison, the parentcompounds, before conversion to the N-oxide, rapidly lose all ability toform a foam during storage.

The N-(Z-hydroxyalkyl)-N-methyltaurine-N-oxides, of this invention areprepared by the oxidation of the correspondingN-(Z-hydroxyalkyl)-N-methyltaurine, according to the following equation:

R and M having the same meaning as given above. While hydrogen peroxideis the preferred oxidizing agent, others 3,l7l,787 Patented Mar. 2, 1965such as ozone, which have been described in the literature for theconversion of amines to amine oxide may be used.

The N-(2-hydroxyalkyl)-N-methyltaurine may be prepared with ease fromstarting materials which are relatively inexpensive and commerciallyavailable, as described in our co-pending application Serial No.116,706, filed June 15, 1961. A desirable method of preparing thesecompounds is by the simple addition of N-methyltaurine to a long chain1,2-epoxyalkane. This simple addition technique produces the desiredN-(Z-hydroxyalkyl-N- methyltaurine, and the reaction product is freefrom inorganic salts which are difficult to remove. Inorganic salts arehighly objectionable, particularly when the compounds are to be used indetergent formulations. The preparation of the epoxide starting materialmay be by conventional methods such as oxidation of the compoundsderived from petroleum sources.

The following examples describe the preparation and characteristics ofthe compounds of this invention, and also illustrate their usefulness asactive ingredients in detergent and dentifrice formulations.

EXAMPLE I A series of the novel compounds of this invention was preparedaccording to the following general procedure.

60 ml. of 30% hydrogen peroxide (0.536 mole) was slowly added to a warmalcoholic solution of sodium N-(Z-hydroxyalkyl) -N-methyltaurine,prepared by dissolving 0.134 mole of sodiumN-(Z-hydroxyalkyl)-N-methyltaurine in 350 ml. of ethyl alcohol. Theresultant solution was maintained at 4050 C. for 24 hours. The excesshydrogen peroxide was then decomposed by placing a 1" x 2" pieces ofplatinum foil into the solution and allowing it to remain there for 2 to4 days. When gas bubbles no longer formed on the surface of theplatinum, it was removed from the reaction solution and the solvent wasevaporated off. The last traces of solvent were removed by drying theresidue at reduced pressure. The residue was finely powdered andsuspended in 200 ml. of acetone. The suspension was warmed to 40 C.,filtered and the product air dried' Final drying was for 6 hours in avacuum oven at 30 mm. and 50 C. Table I lists the compounds preparedwith this procedure.

Table l GENERIC FORIVIULA.

t RCHCHg-N-CHg-CH1SO3NL Where R: Yield (isolated), percent C H 97.5

n -v 14 29 98 o n 97.5 C9H19-C13H27 (mixture) c13H27-C13H37 L.

EXAMPLE II A series of N-(Z-hydroxyalkyl)-N-methyltaurine-N- oxides wasprepared by the method of Example I and tested for detergency by theTerg-O-Tometer Detergency Test. This test gives an empirical measurementof the amount of soil removed from the fabric under simulated washingconditions. Sample swatches of cloth soiled in a standard manner with astandard soil are placed in a miniature washing machine, theTerg-O-Tometer apparatus, and laundered in the presence of a measuredamount of detergent and water of a standard hardness. A Terg-O- Tometerapparatus is described in the Journal of the American Oil ChemistsSociety, vol. 27, May 1950, pp.

tergent was added in the desired amount to the washpot of the machine.1250 ml. of water having a hardness of 180 p.p.m. CaCO (60 partsmagnesium and 120 parts calcium calculated as calcium carbonate) wasadded. The machine was started and the solution agitated until thedetergent was dissolved.

Cloth swatches approximately 4 /2 inches by 6 inches were then added andthe washing was continued for twenty minutes, after which the testswatches were removed from the solution and hand squeezed. The washpotwas refilled with clear rinse water of the same hardness used forwashing at a temperature of 120 R12 R, and, with the agitators running,the cloths were rinsed for 5 minutes. The cloths were then removed, handsqueezed and ironed dry. The reflectance of the cleaned cloths wasmeasured with the Hunter Reflectometer using the green filter.

The Terg-O-Tometer test was carried out in duplicate. The reflectancevalues in the table below represent the average of the actualreflectance readings taken from eight cloth swatches. Each of theN-(2-hydroxyalkyl) -N-methyltaurine-N-oxides was evaluated alone and inthe presence of tetrapotassium pyrophosphate, a conventional builder.Table II summarizes the results obtained.

Table 11 TERG-OTOMETERHOMOLOGOUS SERIES OF SODIUM N (Z-HYDROXYALKYL)-N-METHYLTAUBINE-N-OXIDES OF FORMULA 1 Tetrapotassium pyrophosphate.

EXAMPLE III Sodium N- (2-hydroxyalkyl) -N-methyltaurine-N-oxides wereprepared from sodium N (2-hydroxyalkyl) -N-' methyltaurines, which werein turn prepared by reacting N-methyltaurine witha 1,2-epoxyalkanemixture in which the alkane portion had, in one case, carbon chainlengths ranging from C to C and in the other case, from C to C Themethod of preparation described in Example I was employed. Thesecompounds were evaluated by the Terg-O-Tometer Test, both alone and inthe presence of tetrapotassium pyrophosphate. The mixed alkyl productsshowed slight detergency alone and gave a goodto-excellent response tobuilding. Table III below gives the results of these evaluations.

. Table III TERG-O-TOMETER TESTS OF SODIUM N-(2-HYDROXY-ALKYL)-N-METHYLTAURINE N OXIDES OF FOR- MULA u R-C H-C HgIl]-CH3C Hg-SQQNB.

Reflectance Readings, Hunter Refleetometer with Green Filter Compound0.025% by Level, weight of 0.05% by compoundweight plus 0.05% by weightof 'IKPP 1 R=CgH!9-C13Hz7 mix; 42. 9 48.2 R=C13H27'-'ClBI'I37 mix 42. 651. 0 (Sodium) Dodecylbenzenesulfonate. 42. 9 46. 9 TKPP 1 43. 8 Water4]. 2 Soil Cloth-Initial Average 39. 0

1 Tetrapotassium pyrophosphate.

EXAMPLE IV 7 Three compounds of this invention were evaluated ac- Icording to the RAP Mildness Evaluation Test for Detergents. In thistest, a 2% aqueous solution of the compound was tested on rabbit skinand the results rated according to the following scale.

Table IV below gives the compounds tested and the results of the test.

Table IV Compound Mildness Remarks Rating SodiumN-(2-hydroxydodecyl)-N-Methyltaurine- 0 Epidermis N-Oxlde. normal.Sodium N-(2-hydroxytetradeeyl)-N-Methyltau- 0 Do.

rine-N-Oxide. Sodium N-(2-hydroxyoetadecyl)-N-Methyltau- 0 Do.

rine-N-Oxide.

EXAMPLE v Ingredient: Percent by weight Dicalcium phosphate dihydrate50.00

Other powdered abrasives 5.50 Gum binder .50 Humectant, flavor, andmisc. ingredients 36.15 Glycerine 5.85

N (Z-hydroxytetradecyl) -N-methyltaurine-N- oxide 1 2.00

. 1 Where sodium lauryl sulfate was used, it was added at a level of1.16%, and the glycerine level adjusted to 6.69%.

The toothpaste was thoroughly dispersed by gentle stirring, and thedispersion then transferred to a ml. graduated cylinder. The beaker waswashed with 15 m1. of distilled water and the washings also transferredto the cylinder. The cylinder was then inverted 25 times and allowed torest for 5 minutes before reading the foam volume.

A toothpaste containing 2% ofN-(Z-hydroxytetradecyl)-N-methyltaurine-N-oxide produced a 70 ml. foamvolume in this test as compared with a foam volume of 40 ml. obtainedwith a toothpaste containing a conventional detergent, sodium laurylsulfate, at a level of 1.16%. No change in the foaming power of theN-oxide toothpaste was noted over a one month aging period, while asimilar toothpaste containing N-(2-hydroxytetradecyl)- N-methyltaurineas the detergent, failed to exhibit any foam whatsoever after the sameperiod of storage.

EXAMPLE VI Another important property of toothpaste is freedom fromirritation of mucous membranes. A mucous membrane study was madecomparing the irritation potential of a toothpaste containing N (2hydroxytetradecyl)-N- methyltaurine-N-oxide at a 2% concentration leveland a similar toothpaste containing 1.14% of sodium lauryl sulfate.

A small amount of each toothpaste was applied to the vaginal tissue ofeach of six young adult female rabbits. These were divided into twogroups, one for each formulation, placing three animals in each group.The paste was applied for three consecutive days and observations madeover seven days for signs of irritation to the mucous membrane. Noinflammatory reaction was noticed in either group of rabbits. Theexperimental paste was determined to be without primary irritation.

EXAMPLE VII 6 We claim: 1. A dentifrice composition comprising anabrasive and a compound of the formula wherein R is an alkyl grouphaving from 8 to 18 carbon atoms and M is selected from the groupconsisting of hydrogen and the alkali metals.

2. The dentifrice composition of claim 1, wherein the compound isN-(Z-hydroxydodecyl)-N-methy1taurine-N- oxide.

3. The dentifrice composition of claim 1, wherein the compound isN-(Z-hydroxytetradecyl)-N-methyltaurine- N-oxide.

4. The dentifrice composition of claim 1, wherein the compound is thesodium salt of N-(2-hydroxydodecyl)- N-methyltaurine-N-oxide.

5. The dentifrice composition of claim 1, wherein the compound is thesodium salt of N-(2-hydroxytetradecyl)- N-methyltaurine-N-oxide.

6. The dentifrice composition of claim 1, wherein the compound is onewhere R is a mixture of C to- C alkyl groups.

7. The dentifrice composition of claim 1, wherein the compound is thesodium salt of N-(2-hydroxyhexadecyl)- N-methyltaurine-N-oxide.

8. In a method of cleaning teeth, the step of applying to the surface ofthe teeth, a compound of the formula wherein R is an alkyl group havingfrom 8 to 18 carbon atoms and M is a member of the group consisting ofhydrogen and the alkali metals.

References (Zited in the file of this patent UNITED STATES PATENTS2,191,199 Hall Feb. 20, 1940 2,465,737 Martin Mar. 29, 1949 2,618,607Sanders Nov. 18, 1952 2,618,608 Schaeifer Nov. 18, 1952 2,694,727 Crossat al Nov. 16, 1954 2,697,116 Stayner Dec. 14, 1954 2,812,284 SandersNov. 5, 1957 2,830,082 Sexton et a1. Apr. 8, 1958

1. A DENTIFRICE COMPOSITION COMPRISING AN ABRASIVE AND A COMPOUND OF THEFORMULA